Or check many of the other posts citing HD700 as having neither the technical prowess of HD800 nor the organic fluidity of HD650, and with all the bite of a Grado

I don't have HD700, I can't tell you if it's "moar better" or not. I can say that a simple look at the driver design shows it to be forged from the same basic designs as the 6xx (I'm not saying it's the same driver, same magnets, same diaphragm material etc, only that it's built upon the same general design versus the "all new tech" of the HD800.) I can also say that a simple look at the FR charts should show you despite whether it's worse or better, it's quite simply different. It's not "a better HD650" but an entirely different sounding headphone emphasizing a more aggressive upper-mids & treble rather than the lush emphasized mids of the HD650.

For folks who feel something is wrong with HD650 and want to "fix" (brighten/move-forward) it, HD700 may be a route to go. If you really love HD650, and it sounds like you do, odds are you may not love HD700 since it tries to be so opposite the signature of HD650. If you really love HD650 with the Cardas cable, which is in itself warm, that means you're a warm+warm fan....and HD700 sounds very very wrong for that unless you want something to complement HD650 with.

If you're looking for an "upgrade" with a similar sound to HD650, HE-500, LCD-2 may be more in line. Though I'm not certain HE-500 is truly an upgrade as much as an alternate.

If you're looking for an "upgrade" from something made by Sennheiser, HD800 may be the ideal route. Though it's also very different from HD650 as any FR chart will show.

Despite some people saying the HD700 is "better" it would be almost impossible to compare two radically different FR's like that. It would seem more detailed just because of the treble peaks, just as HD650 notoriously seems less detailed than it actually is due to the absence of some of that treble and any treble peaks. If the driver is the same design and the same size the only way it could be "more detailed" is if the magnets were stronger, the voice coil a different material, and the diaphragm denser, lighter. That may all be true, but it would be hard to dell because the presentation itself draws attention to detail that HD650 draws attention away from. That's not true of just HD700, but the nature of brighter/peakier headphones versus warmer headphones. Think back to the DT880 vs HD650 debates of old. IMO HD650 and HD700 aren't so much "upgrade/downgrade" models, but two models for different buyers that happen to be very poorly priced. 10 years ago the buyer willing to dump $500 on a headphone was seeking warm organic sound. Today the buyer willing to dump $1000 on a headphone is seeking bright detail-accentuated sound. While not a true "u" or "v" HD700 could probably be described as Sennheiser's "fun" can.

If you just want to enjoy very detailed music, close your eyes, and put the HD650s on